The present invention relates to a fusion apparatus which in order to prevent the occurrence of a fire due to an abnormality such as that which occurs at the time of a collision accident of the vehicle, etc. cuts off by fusion a low melting point element such as a fuse installed in an electric circuit when an abnormality happens in a vehicle, and a circuit breaker including the same.
Generally, in an electric circuit for an automobile, a fuse or a fusible link is used in order to instantaneously break the circuit when an excess current or short-circuit current has occurred.
However, a fuse or fusible link is one that is intended to break the circuit after the occurrence of an excess current. Therefore, it is impossible to compulsively break the circuit with an arbitrary timing. Accordingly, in order to prevent a fire caused by a spark that occurs from part of the electric circuit from being taken on a fuel, etc. which has leaked due to a collision accident of the vehicle, or the like, it was necessary to compulsively break the electric circuit from the outside.
Also, most of the recent automobiles are arranged to have their inside operated with the use of a computer system and the electric circuit involved also is wired in a complicated way. Therefore, the probability that a spark occurs due to a breakage or short-circuits of the electric wire at the time of a collision of the vehicle is becoming high. For this reason, in order to prevent the occurrence of a fire, etc., it was necessary to break the circuit at a position near to the power source.
As a technique of compulsively breaking the electric circuit, there is a circuit breaker which breaks, utilizing the explosion force of explosives, a breakage portion installed at part of the conductor and thereby breaks the electric circuit (see Japanese Patent Application Laid-Open Publication No. H10-55742).
The circuit breaker includes a cylindrical portion having an opening portion, an explosive inside the cylindrical portion, a filament inside the cylindrical portion which causes a firing of the explosive by way of an external power source, a breakage portion which makes connection between the conductors in front of the opening portion, and a cover portion which resists broken pieces due to a breakage having taken place due to the explosion force of the explosive and which resists a rapid rise in pressure.
In this circuit breaker, by causing the flow of a current the quantity of which is larger than prescribed, the explosive is exploded, and, by the resulting explosion force, the breakage portion in front of the opening is compulsively broken. Accordingly, it is possible to arbitrarily select the timing at which to cause the flow of the current into the filament, through a control circuit, and therefore to break the electric circuit as the occasion demands.
On the other hand, as a technique related to the fusion of a fuse, there is known a fuse described in Japanese Patent Publication No. 59-48505. A perspective view of this fuse is made in FIG. 1 and a sectional view taken along a line II--II of the fuse illustrated in FIG. 1 is made in FIG. 2.
As illustrated in FIGS. 1 and 2, a capsule 104 in which a fuse conductor dissolving agent 105 is sealed, is disposed within a fuse vessel 101. Due to the generation of heat from a fuse conductor 103, the capsule 104 is heated. When this heated temperature has reached a prescribed temperature not higher than a fuse conductor fusion temperature, the capsule 104 is fused and destroyed.
As a result of this, at the time of a short-circuit accident, even if the current which flows into the fuse conductor 103 is smaller than a rated magnitude of fusion current, the fuse conductor 103 can be reliably cut off by fusion.